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Clansman
Tux's lil' helper
Joined: 10 Jan 2004
Posts: 140
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 Posted: Thu Oct 14, 2004 1:20 pm Post subject: kernel module programming question |
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hi everyone,
not sure if i'd post here or in kernel & hardware. can't harm putting it here.
i made a very simple kernel module that creates a /proc file and it counts the number of accesses to itself.
the problem is that the counter gets incremented by steps of 2 or 3 instead of 1.
i mean catting the file once i get counter value=1, then catting it again i get counter value=4 and so on...
stracing the "cat /proc/new/info" results in 1 open of the file and one read. still those are 2 accesses and not 3. to be sure i made a program that just opens and closes the file to see if the counter got updated. it didn't...
what could be happening here?
thanks.
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Athas
Guru
Joined: 04 Sep 2003
Posts: 394
Location: Brøndby, Denmark
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Clansman
Tux's lil' helper
Joined: 10 Jan 2004
Posts: 140
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| Posted: Thu Oct 14, 2004 2:39 pm Post subject: |
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feedback 
ok, i could post the entire code but that would be big. i'd start by the read_proc function:
| Code: |
/*
* read_proc function
*
*/
static int hackalot_proc_info (char *page,char **start,off_t off,int count,int *eof,void *data)
{
int size;
/* just print information */
size=sprintf(page, "%s %d %s\n",HACKALOT_INFO_D1,counter,HACKALOT_INFO_D2);
if(size>0)
++counter;
return(size);
}
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right now it's a bit different. the counter variable is properly locked via atomic operations and the size>0 check is no longer. it doesn't make a difference.
still the behaviour is not the expected.
thanks. |
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